In imaging apparatuses such as a digital video and a digital camera, a subject image is formed on an imaging device such as a CCD or a CMOS via a lens, whereby a subject is converted into two-dimensional image information. Patent documents 1 and 2 have proposed an example of a single-eye camera module. Also, Patent document 3 has proposed an example of a camera module that uses two objective lenses to enable three-dimensional observation.
On the other hand, in order to reduce the size and thickness of a camera module, a compound-eye camera module has been proposed.
Patent document 4 describes an example of the compound-eye camera module. In Patent document 4, an imaging optical system has a configuration in which a lens devoted to red wavelength light, a lens devoted to green wavelength light and a lens devoted to blue wavelength light are arranged in a plane. An imaging device is provided with imaging regions for the respective wavelength bands corresponding to the respective lenses.
Thus, the wavelengths of light to which the individual lenses are devoted are limited. This makes it possible to form a subject image on an imaging plane using the single lenses, thereby reducing the thickness of the imaging apparatus considerably.
FIG. 7 is an exploded perspective view showing an imaging system of the conventional camera module as described above. A diaphragm member 111, a lens array 112, a light-shielding block 113, an optical filter array 114 and an imaging device 116 are arranged in this order from the subject side. The lens array 112 includes a plurality of lenses 112a. The diaphragm member 111 includes diaphragms (openings) at positions that coincide with optical axes of the respective lenses of the lens array 112.
The optical filter array 114 includes a plurality of optical filters 114a that have different spectral characteristics for regions corresponding to the respective lenses of the lens array 112 and covers a light receiving surface of the imaging device 116. The light-shielding block 113 includes a light-shielding wall 113a at a position that coincides with each border between the adjacent lenses of the lens array 112, namely, the border between the adjacent optical filters 114a of the optical filter array 114. The imaging device 116 is placed on a semiconductor substrate 115. On the semiconductor substrate 115, a driving circuit 117 and a signal processing circuit 118 also are mounted.
With this camera module, by the light-shielding wall 113a of the light-shielding block 113, it is possible to prevent light that has passed through a certain lens 112a from entering the imaging region that does not correspond to this lens 112a. 
However, when an incident angle of a light beam entering the lens 112a increases, the light beam that has passed the lens 112a also has an increased angle accordingly. In the camera module shown in FIG. 7, the light-shielding wall 113a is arranged above the imaging device 116 via the optical filter 114a so as to be substantially in parallel with the optical axis.
Therefore, although a light beam with large incident angle whose image forming position is displaced greatly from the imaging region does not enter the imaging region directly, it is reflected by the light-shielding wall 113a, leading to a problem that a reflected image is formed on a captured picture in the imaging region.
Further, when a hood that restricts the angle of a light beam entering the lens 112a is provided on the subject side in order to remove a ghost image due to this reflection, the height of the camera module increases. On the other hand, when the imaging region is set so that the reflected image is not formed in the imaging region, there is no alternative but to use an imaging device with the unnecessarily large number of pixels or to use a smaller imaging region. In this case, there have been problems of increased cost and lowered performance.
Patent document 1: JP 2002-118776 A
Patent document 2: JP 2 (1990)-106847 U
Patent document 3: JP 9 (1997)-127435 A
Patent document 4: JP 2003-143459 A